The invention relates to a system for reproduction machine control, and more particularly, to the resetting of control element nodes and the minimization of communication failure impacts among the nodes for such machines.
In any complex control system, there is usually a large number of machine problems that can cause the control system to temporarily malfunction. These problems can be noise or any number of software and hardware related malfunctions or crashes. When a crash or system abnormality occurs, the system must be reset and resynchronized. In a multiprocessor control this means resynchronizing the operation of the various processors or nodes. This can include various complex resetting procedures and even require manual intervention.
In a copier/duplicator with a local communications network having a plurality of control elements or nodes, there always exists the possibility of a communication failure. If a communication failure does occur, it is important to minimize the impact of the failure on the rest of the communication network.
It would be desirable, therefore, to provide a means to localize a communications failure to one specific control board or node to minimize the impact on the communications network.
In the prior art there are examples of resetting the control of a machine. For example:
U.S. Pat. No. 4,589,090 to Downing et al., assigned to Xerox Corporation, discloses a remote processor crash recovery method wherein a fault can be detected and reset. A means is provided to isolate a fault and reset only that board so that machine operation is not interrupted. See Col. 6, lines 50-52. If a control board faults and cannot be reset, the machine will continue to run if the board is not essential to the machine. See Col. 6, lines 62-65.
U.S. Pat. No. 3,818,199 to Grossmann et al. discloses a method and apparatus for processing errors in a data processing system wherein an error can be isolated and localized to a process and then tested. See Col. 5, lines 25-32. A means is provided to let another processor take over a process assigned to a faulty processor. See Col. 5, lines 9-17.
U.S. Pat. No. 4,789,985 to Akahoshi et al. discloses a document processing apparatus having fault detection which runs a self-diagnostics test to check each resource. See Col. 5, lines 53-55. A means is provided to transfer a process from a faulty resource to an available alternative.
U.S. Pat. No. 4,320,508 to Takezoe discloses a self-diagnosing, self-correcting communications network wherein a network senses a fault and reconfigures itself appropriately. See Col. 3, lines 10-13. A means is provided to test a node for a fault by sending out a series of pulses. See Col. 3, lines 14-19. A means is also provided to catalog a fault.
A difficulty with the prior art systems is that the reliability thereof rapidly diminishes if for every communication fault detected, the reset procedure must respond as if the entire machine is affected. Another difficulty in prior art systems is the need of a designated master processor to reset the other processors and the need for separate reset lines to each of the processors. It would be desirable to be able to provide a simple and relatively inexpensive method to reset and recover from a communication fault.
It is an object, therefore, of the present invention to provide a method for each node or element of a control to reset itself independently of all other nodes or elements of the system in response to a communication failure. It is another object of the present invention to provide a method for each node or element of a control to be oblivious to a communication failure in any other node and to continue in normal operation. Other advantages of the present invention will become apparent as the following description proceeds, and the features characterizing the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.